A transfer mechanism is connected to a transmission of a vehicle and the difference between the rotating forces applied to the front and rear wheels is adjusted by the transfer mechanism.
For instance, a rear differential gear is connected to a rotational shaft of the transfer mechanism through a propeller shaft. The rotating force is transferred to the rear wheels by the rotational shaft.
The transfer mechanism has a transfer shaft having a gear on one end. Lubricating oil which is lifted up by the gear is supplied to a bearing portion of the rotational shaft. On the other hand, a final deceleration gear of the differential gear mechanism is in engagement with the other end of the transfer shaft, thereby transferring the driving force from the transmission to the transfer shaft.
A known transmission for 4-wheel drive is disclosed in JP-B-63-39450. According to a power unit for a vehicle disclosed in the above document, a subtransmission mechanism comprises: a subshaft whose both end portions are rotatably supported between a side wall of a clutch casing and a transmission casing and which is arranged in parallel with input and out shafts; an intermediate shaft whose both end portions are fitted and supported; a subinput gear which is rotatably fitted to the intermediate shaft; a suboutput gear which is fixed to the subshaft; a deceleration input gear which is integratedly formed on one side of the subinput gear; a deceleration output gear; and a synchronizing mechanism, wherein a subtransmission mechanism which can obtain a large deceleration ratio without changing the existing transmission and a vehicle body structure is additionally provided and assembling the subtransmission mechanism is easy.
Another known apparatus is disclosed in JP-B-1-16687. According to the 4-wheel driving apparatus disclosed in the above document, in a driving apparatus which realizes a common use of the parts for 4-wheel driving and 2-wheel driving by fixing a transfer casing to a clutch housing by bolts in at least a part of the transfer casing so as to face the edge surface which extends in the front and rear directions of the vehicle body in the side portion of the engine side of an enclosing portion of a front differential gear of the clutch housing, a large enough degree of freedom for a motive power transfer system is assured with respect to an arrangement of a mechanism to extract an output for driving the rear wheels while avoiding an interference with the engine.
In a conventional transmission for 4-wheel drive, as shown in FIG. 5, a transmission 102 has: a front side differential gear 104; a transfer mechanism 106; a transmission side input shaft 108 serving as an input shaft of a gear transfer system for inputting a driving force from an internal combustion engine (not shown); and a counter shaft (not shown) serving as an intermediate shaft for transferring the rotating force of the transmission side input shaft 108 to the differential gear 104.
The transmission 102 is coupled with the differential gear 104 for rotating the front wheels (not shown) via a drive shaft.
The transfer mechanism 106 which is coupled with the differential gear 104 has therein a transfer shaft 110. A bevel gear 112 is provided on one end of the transfer shaft 110 and a driven gear 114 is provided on the other end. Thus, the transfer mechanism 106 distributes the driving force of the internal combustion engine, which driving force is transferred from the transmission 102 through the driven gear 114 as engaged with a final deceleration gear 116 on the front side differential gear 104, and ultimately to a rotational shaft 118 through the bevel gear 112. The driving force which is output from the rotational shaft 1 18 is transferred to the rear wheels (not shown) via a propeller shaft (not shown) connected through a coupler 120, a rear side differential gear, and the like.
As will be obvious from FIG. 5, when a transmission casing 122, a clutch housing 124, and a transfer casing 126 are coupled together, an internal space portion of the transmission 102 is also coupled, thereby forming one internal space. Lubricating oil is supplied into this one internal space, thereby accomplishing lubrication in each portion.
However, when the transfer mechanism is lubricated by using an ATF (automatic transmission fluid or oil) of low viscosity, there are inconveniences such that the required quantity of the ATF is large, the quantity of the ATF changes remarkably, the temperature of the ATF easily rises, and an absence of lubricating oil occurs at the engaging portion of each gear such as a bevel gear or the like and in the bearing portion, so that a defective lubricating state is caused.
On the other hand, in a manual operating type transmission, when a lubricating oil of high viscosity is used, there are inconveniences in that the lubricating oil is attracted by the differential gear which is rotated in association with the rotation of the transmission, the lubrication of the transfer mechanism is not sufficiently executed, and the synchronizing mechanism of the transmission is lubricated by the high viscosity lubricating oil, so that the shift feeling is increasingly influenced such that it deteriorates.
To eliminate the above inconveniences, it is therefore an object of the present invention to provide a transmission for 4-wheel drive in which a final deceleration differential gear is coupled with the 4-wheel drive transmission, a transfer mechanism is coupled with the differential gear, and an oil sealing portion is formed on a shaft of the transfer mechanism to partition and separate the transfer mechanism from the differential gear. The inside of the transmission can thus be separately partitioned into two separate portions, so that lubricating oils of different viscosities are respectively supplied to those separate portions, and lubrication can be efficiently performed.
According to the invention, in a transmission for 4-wheel drive having a transfer mechanism for adjusting the difference between rotating forces applied to the front and rear vehicle wheels, a final deceleration differential gear is coupled with the transmission; a transfer mechanism is coupled with the differential gear; and an oil sealing portion is formed on a shaft of the transfer mechanism to partition and separate the transfer mechanism from the differential gear.